1. Field of the Invention
The invention relates to a laser rangefinder and, in particular, to a laser rangefinder that can measure distances in dual directions.
2. Description of Related Art
The existing method of measuring the distance between two objects that are far apart (e.g., the distance between two opposite walls or from the floor to the ceiling in a room) usually involves the user of a tape measure. However, the tape measure has to touch against the two end surfaces of the two objects whose distance in between is of interest. Moreover, the tape measure has the problem of flexibility and measuring errors. When the ceiling is too high, the tape measure may have the problem of unable to reach the ceiling. Therefore, one encounters the problems of insufficient length, inconvenience in usage, and/or large errors when using the tape measure to measure the distance between two objects.
When using a laser rangefinder to measure the distance between two objects, one normal put the laser rangefinder against one of the end surfaces (e.g., the floor). The laser rangefinder emits a laser beam toward the other end surface (e.g., the ceiling) and receives the reflected laser beam from the end surface (i.e., the ceiling). By measuring the difference between the emission time and reception time of the laser beam, the distance between the two objects can be calculated. However, the current laser rangefinder requires that the laser beam be perpendicular to the end surface. This easily results in measuring errors. Besides, one has to put the laser rangefinder against one of the end surfaces in order to measure the distance to the other end surface. This is quite inconvenient in practice.